1. Field of the Invention
This invention relates generally to commodity bags, and more specifically to a sealable commodity bag including a venting means allowing for air to escape from the bag after closure.
2. Description of the Prior Art
Commodity bags are widely used in industry for storing a variety of dry powdery or granular products. Food products such as powdered milk and the like require a closure that resists moisture and contaminants from entering the bag. Most of the commodity bags commonly used for dry foods include an interior plastic bag or liner combined with several outer plys of paper. Such bags are formed by folding flat material into a tube with overlapping margins and sealing the margins together with heat seals or glues, then folding and sealing one end of the tube to form a bag, which is then similarly folded and sealed at the other end after filling. The multiple plys of paper with the plastic result in a very strong and burst resistant container that may be air tight.
One problem that arises from this type of container is that air and possible other gasses may be easily trapped within the bag along with the contents. Several condiment bags have been developed that allow air to escape after closure. Some of the methods used in these designs somewhat discourage moisture and contaminants from entering the bags.
Perry (U.S. Pat. No. 3,302,859) discloses a method allowing air to pass through crescent shaped holes in a bag. The most effective version of this bag locates the cuts, or vents, along the margin of overlapping materials and between two heat seals wherein the vents formed through one layer of the overlapping margins are misaligned with the vents formed through the opposing layer. The intention is that the opposing layer of material will lie against and thereby close off the vents once air is pressed from the bag. This design is problematic in that the flexibility and distortability of the plastic material, and the repeated handling of the bag all effect the reliability of this method especially where the contents can easily pass through the vents.
Kenan (U.S. Pat. No. 4,470,153) discloses an improvement in venting where a strip of paper or filter like material is sealed within the margin between two seals. The filter material is then incorporated into the end seals thereby creating a filtered path for air to pass. The practicality of this design comes into question as well as the ease of manufacturing. This design may also encourage moisture to enter the bag if the filter is absorbent.
Keppel (U.S. Pat. No. 4,550,441) provides a more practical and practiced method wherein channel formed between two heat seals along overlapping margins include distally separated vent holes formed through each of the overlapping layers, wherein one of the vent holes is formed through the inner layer (into the bag interior) and the other vent hole is formed through the outer layer. Air, contents, and contaminants must travel a course through the channel to enter or exit the bag. The relative effectiveness of this method is proven in practice, though the vent holes must be punctured through the bag, and the puncture holes are small and easily obstructed.
By careful examination of these methods, it should be clear that the further the distance that separates the vent holes, the more effective the method. It can also be concluded that the effectiveness of these methods to inhibit or prevent the entry of contaminants and moisture and the re-entry of air can be influenced by the distortions, movement, turning and positioning of the bag relative to gravitational and other forces to which the bag and it's contents may be subjected.
What is needed is an improved vented bag that does not require punctured or cut holes through the bag surface.
What is also needed is a sealed bag with an improved means of venting which discourages or greatly inhibits the movement of moisture and particles through the venting means especially where the bag may be subjected to turning, handling and forces of nature.